1. Technical Field
This invention relates to network connectivity between host computer systems over storage area networks (SANs) using the SAN's network protocol such as the FICON protocol.
2. Description of the Prior Art
Network architecture is a blueprint that is used to guide the design and implementation of networks. These blueprints are used because networks are not fixed at a single point in time, but evolve to accommodate changes in both the underlying technologies upon which they are based as well as changes in the demands placed on them. The primary function of a network is to provide general cost-effective, robust and high-performance connectivity among a large number of computers.
Channels and networks are the two primary ways that data is transferred between devices such as processors, and peripherals such as printers. Channels transfer data through switched or direct point-to-point connections and they work by creating a fixed connection between the source and destination devices until the transfer is complete. Channels transfer data at high speeds and are very economical. Networks, on the other hand are collections of nodes such as processors, print devices and workstations. Connections on networks are slower than those made via channels. Channels work best among few devices, and connect via predefined addresses. Networks, on the other hand, can handle multiple requests among multiple connections. Fibre Channel (FC) is a hybrid of both network and channel methods and combines the best aspects of both.
Host to host connectivity within a high-speed network environment is typically accomplished by using several different types of network media. Network media include Token Ring and Ethernet and other topologies. Token Ring is a physical network technology in which hosts are connected in a ring. A token (bit pattern) circulates around the ring and a given node must possess the token before it is allowed to transmit. Token Ring has a bandwidth of 4 and 16 Mbps (megabits per second). Fiber Distributed Data Interface (FDDI) is a high-speed token ring networking technology designed to run over optical fiber. The cables used for the token ring network are attached to adapters instead of the hosts themselves. Ethernet is a network technology that uses CSMA/CD (Common Sense Multiple Access) and has a bandwidth of 10 Mbps or 100 Mbps. The Ethernet protocol is implemented in hardware on the network adapter.
A SAN is a dedicated, centrally managed, secure information infrastructure which enables any-to-any interconnection of servers and storage systems. SANs allows for connection between storage devices and host machines across greater distances than are possible on a traditional local area network (LAN). SANs enable users to store large volumes of data at remote locations called libraries. SANs are rapidly being integrated into distributed environments using Fibre Channel technology.
Fibre Channel (FC) is a high speed (1.06 Gbps) medium used for data transfer and storage. It is essentially a serial data channel created over fiber optic cabling. Fibre Channel provides a logical bi-directional, point to point connection between a host and a device. Just as existing networking technologies using LAN/WAN (Local-Area-Network/Wide-Area-Network) utilize configurations connected to PCs, servers, print and storage devices, so too does FC. However, because FC uses fiber optic cabling, connections along a FC network are possible. Another feature of FC is its ability to provide increased bandwidth over communications channels.
ESCON (Enterprise Systems Connection) is a fiber-based protocol. The ESCON protocol allows various emulations to run on top of it for further communication with the mainframe either directly or indirectly through ESCON emulators. However, in order to perform this connectivity, the non-mainframe hosts need a separate ESCON hardware adapter, as well as other limitations.
ESCON based physical channel speeds are 17 Mbps. ESCON network connectivity is usually accomplished through ESCON directors and hence the distances between the end-hosts are limited. ESCON requires a repeater every 1.86 miles. This requirement leads to increased costs when the machines or hosts that are to be connected are far apart.
By comparison, FICON (Fibre Connectivity) Channel is a protocol that is targeted to provide high-speed storage Input/Output (I/O) capability. FICON provides a theoretical throughput of 100 Mbytes/sec, which allows it to be used in a SAN (Storage Area Network) environment.
Addressing the need for a centralized storage management solution across heterogeneous networked resources, FC SAN architecture benefits a typical networked environment by delivering a dedicated storage environment, and by using of high-speed fiber-optic or copper cabling to interconnect servers, workstations and storage devices.
As a data-channel network standard, the FC backbone of a SAN environment contains the network features that provide connectivity, distance and protocol multiplexing.
Because FC SANs are protocol-independent, the support for network protocols like Tansmission Control Potocol/Iternet Potocol (TCP/IP) and audio/video is accomplished with a single physical layer. FC allows concurrent communication among workstations, mainframes, servers, data storage systems and other peripherals using SCSI and IP protocols. The interconnectivity of computers and storage devices forms the basis of a SAN.
Although FC SAN is a fiber-based solution for high-speed storage access, there remains an industry need for high-speed, host to host connectivity that is an improvement upon the existing ESCON based architecture.